Device for purifying the exhaust gas of an internal combustion engine to reduce the nitrogen oxide content

ABSTRACT

A device for purifying exhaust gas of an internal combustion engine, to reduce the nitrogen oxide content, which has an exhaust conduit for introducing part of the exhaust gas into an intake passage of the engine, a valve provided in the exhaust conduit opened by a diaphragm device to allow passage of the exhaust gas when the vacuum acting on the diaphragm device becomes over a predetermined value, a vacuum conduit for introducing the vacuum of the intake passage of a carburetor into the diaphragm device, said vacuum conduit being connected to the intake passage at a position adapted to open upstream of the throttle valve when the throttle valve is closed and to open downstream of the throttle valve when the throttle valve is slightly opened, control means operating to sense the engine temperature and provided in the vacuum conduit, said control means introducing the intake vacuum into the diaphragm device when the sensed temperature is over a predetermined value and for shutting off the introduction of the intake vacuum into the diaphragm device when the sensed temperature is below a predetermined value whereby the part of the exhaust gas is introduced into the intake passage only when the engine temperature becomes over a predetermined value and the intake vacuum becomes over a predetermined value.

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[ 1 Mar, 14, 1972 [72] Inventors: Takumi Muroki; Motoyuki lllayashida,

both of Hiroshima-ken, Japan [73] Assignee: 'lloyo Kogyo Company Limited, Azashinchi, Fuchu-cho,, Akigun, Hiroshimaken, Japan [22] Filed: Oct. 8, 1970 [21] AppLNo; 79,1108

3,512,509 5/1970 Daigh ..123/119 A Primary Examiner-Mark M. Newman Assistant Examiner-11. B. Rothman Attorney-Sughrue, Rothwell, Mion, Zinn and Macpeak [5 7] ABSTRACT A device for purifying exhaust gas of an internal combustion engine, to reduce the nitrogen oxide content, which has an ex haust conduit for introducing part of the exhaust gas into an intake passage of the engine, a valve provided in the exhaust conduit opened by a diaphragm device to allow passage of the exhaust gas when the vacuum acting on the diaphragm device becomes over a predetermined value, a vacuum conduit for introducing the vacuum of the intake passage of a carburetor into the diaphragm device, said vacuum conduit being connected to the intake passage at a position adapted to open upstream of the throttle valve when the throttle valve is closed and to open downstream of the throttle valve when the throttle valve is slightly opened, control means operating to sense the engine temperature and provided in the vacuum conduit, said control means introducing the intake vacuum into the diaphragm device when the sensed temperature is over a predetermined value and for shutting OK the introduction of the intake vacuum into the diaphragm device when the sensed temperature is below a predetermined value whereby the part of the exhaust gas is introduced into the intake passage only when the engine temperature becomes over a predetermined value and the intake vacuum becomes over a predetermined value.

4 Claims, 3 in Figures Patented March 14, 1972 3,648,672

THROTTLE VALVE OPENING 0 4 V2 4 l l l INVENTORS mum MOROKI A MOTOYUKI HAYASHIDA ATTORNEYS DEVICE FOR PURIlFTING THE EXHAUST GAS OF AN INTERNAL COMBUSTION ENGINE TO REDUCE THE NITROGEN OXIDE CONTENT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a device for purifying the exhaust gas of an internal combustion engine for the purpose of removing nitrogen oxide therefrom, and more particularly to a device adapted to introduce part of the exhaust gas into an intake gas mixture and shutting it off for the purpose of removing unburned detrimental components and the nitrogen oxide, while maintaining engine performance in response to three operating conditions of the internal combustion engine. More specifically, the three conditions are warm-up (the operating time from when the engine is started to when the engine reaches normal temperature), post-warm-up, which is also divided into deceleration, idling, low speed, low load, and high speed, high load (when the intake vacuum is below a predetermined value) and normal operating time (when the intake vacuum is over a predetermined value) such as acceleration, intermediate operation, part load operation, except the aboveidentified operations.

2. Description of the Prior Art In general, since the mixture rate of fuel is relatively large while the internal combustion engine is idling or decelerating or in full load operation, the nitrogen oxide content of the ex haust gas being discharged from the internal combustion engine is low at this moment. On the other hand, since the mixture rate of fuel relatively small as the internal combustion engine is accelerating or in an intermediate speed or a part-load operation, the nitrogen oxide content of the exhaust gas is high during these operations. The nitrogen oxide content of the exhaust gas of an engine which is sufficiently warmed-up is greater than that of exhaust from an engine which is not sufficiently warmed-up during the warming-up operation. It is already well known that if part of the exhaust gas discharged from the internal combustion engine is introduced into the intake gas mixture so as to lower the combustion efficiency of the fuel, the nitrogen oxide becomes reduced. However, if part of the exhaust gas in introduced into the intake gas mixture regardless of the operating condition of the internal combustion engine as a conventional engine, the combustion of the fuel becomes extremely bad so that it detrimentally affects the operability of the internal combustion engine so as to extremely deteriorate the utility thereof, particularly during idling or deceleration of the engine, such that the nitrogen oxide contained within the exhaust gas is extremely small.

It is, therefore, an object of the present invention to provide a device for purifying the exhaust gas of an internal combustion engine and particularly to reduce the nitrogen oxide content of the unburned detrimental components contained within the exhaust gas which may control the introduction of part of the exhaust gas into the intake gas mixture in response to three operating conditions of the engine; which are wannup; deceleration, idling, low speed low load, and high speed high load after the warm'up; and normal operation except the above specified conditions.

It is another object of the present invention to provide a device for purifying exhaust gas of an internal combustion engine for particularly reducing the nitrogen oxide content in which the coolant temperature or the exhaust gas temperature of the engine (called the engine temperature) is detected by a thermo sensor, the intake vacuum is detected at an opening of a vacuum tube to an intake gas passage disposed in up-stream of the throttle valve when the throttle valve is closed while disposed in down-stream of the throttle valve when the throttle valve begins to open, whereby the aforementioned three operating conditions are detected when said engine temperature changes with respect to a predetermined value and said intake vacuum changes with respect to a predetermined value, and part of the exhaust gas is controlled to be introduced into the intake gas mixture in response to the sensed operating condition.

It is a further object of this invention to provide a device for purifying exhaust gas of an internal combustion engine which may cool the exhaust gas introduced into the intake gas mixture so as to prevent it from deteriorating the engine due to its high temperature and to improve the endurability thereof.

Other objects, features and advantages of the present invention will become apparent from the following description.

SUMMARY OF THE INVENTION A device for purifying exhaust gas of an internal combustion engine, to reduce the nitrogen oxide content, which has an exhaust conduit for introducing part of the exhaust gas into an intake passage of the engine, a valve provided in the exhaust conduit opened by a diaphragm device to allow passage of the exhaust gas when the vacuum acting on the diaphragm device becomes over a predetermined value, a vacuum conduit for introducing the vacuum of the intake passage of a carburetor into the diaphragm device, said vacuum conduit being connected to the intake passage at a position adapted to open upstream of a throttle valve when the throttle valve is closed and to open downstream of the throttle valve when the throttle valve is slightly opened, control means operating to sense the engine temperature and provided in the vacuum conduit, said control means introducing the intake vacuum into the diaphragm device when the sensed temperature is over a predetermined value and for shutting off the introduction of the intake vacuum into the diaphragm device when the sensed temperature is below a predetermined value whereby the part of the exhaust gas is introduced into the intake passage only when the engine temperature becomes over a predetermined value and the intake vacuum becomes over a predetermine value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view of the device of this invention for purifying exhaust gas used in a reciprocating piston internal combustion engine;

FIG. 2 is an explanatory view of the operation of the control means used in the device shown in FIG. ll; and

FIG. 3 is a graphical representation of the relationship between the opening of the throttle valve and the intake vacuum.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be described with reference to the drawings showing one embodiment of this invention adapted for the reciprocating piston internal combustion engine.

Reference numeral 1 in FIG. 1 designates a cylinder, 2 a cylinder head, 3 a piston moving in reciprocating motion within the cylinder I, and 4 a coolant passage provided in the cylinder l and cylinder head 2 for passing the coolant. 5 and 6 illustrate a choke valve and throttle valve, respectively disposed in an intake passage 7 of a carburetor, 8 shows an intake port provided in the cylinder head 2, and 9 an inlet manifold for communicating between the intake passage 7 and the intake port 8.

l0 designates a device for purifying unburned detrimental components such as carbon monoxide or hydrocarbons in the exhaust gas which is installed to the cylinder head 2 so that it communicates with the exhaust gas port 111 of the cylinder head 2. [2 denotes an air pump driven by the engine for supplying secondary air into the exhaust gas passing through the exhaust port 11 so as to improve the purity of the exhaust gas within the device 10 for purifying the exhaust gas. 13 illustrates a cooling chamber of branched exhaust gas provided in the inlet manifold 9 for cooling the branched exhaust gas introduced from the exhaust port 11 through a branch conduit I4 by the latent heat of vaporization of the fuel passing through the inlet manifold 9. l5 depicts a drain valve in the cooling chamber 113 for exhausting the moisture generated due to the condensation of the branched exhaust gas when the branched exhaust gas is cooled within the cooling chamber I3. 16 illustrates a valve for controlling the branched exhaust gas flow connected to the cooling chamber 13 through a pipe 17, and 18 is a filter disposed in pipe 17 for filtering the impurities contained within the exhaust gas. 19 designates a conduit for introducing the branched exhaust gas from pipe 17 into the intake gas mixture, which conduit is connected at one end to the valve 16 and is projecting at the other into the inlet manifold 9;20 is a diaphragm device for operating the valve 16.

21 illustrates a control device installed to the cylinder 1, 22a temperature sensor of the control device 21 which is disposed into the coolant in the coolant passage 4;23 is a vacuum control valve to which the operation of the sensor 22 is transmitted through the rod 24 and which has a vacuum hole 25 bored therein and annular left and right seals 26 and 27 disposed on the outer periphery thereof. 28 is a-vacuum conduit which is at one end disposed upstream of the throttle valve 6 when the throttle valve 6 is fully closed, while being disposed downstream of the throttle valve 6 when the throttle valve slightly opens in connection with the intake passage 7 so as to detect the vacuum characteristics as shown in FIG. 3.

The other end of the vacuum conduit 28 is so connected to the control device 21 that it communicates between the left and right seals 26 and 27 when the vacuum control valve 23 is disposed in the rightward position as shown in FIG. 2 while it communicates with the right portion of the right seal 27 when the vacuum control valve 23 is disposed in the leftward position as shown in FIG. 1. 29 is an outlet to the atmosphere which is so disposed to the leftward portion of the left seal 26 when the vacuum control valve 23 is disposed in rightward, while between the left and right seals 26 and 27 when the vacuum control valve 23 is disposed in the leftward.

30 illustrates a vacuum conduit connected at one end to the diaphragm device 20 while connected at the other end to the control device 21 so as to be disposed to the leftward of the left seal 26 regardless of the position of the vacuum control valve 23. When the vacuum of the vacuum conduit 30 is below a predetermined value, the diaphragm device 20 does not operate to close the valve 16 while if the vacuum of the vacuum conduit 30 increases over a predetermined value, the diaphragm device 20 operates to open the valve 16.

When the engine is operated so that the temperature of the coolant in the engine is below a predetermined value such as, for example, 60 C., the vacuum control valve 23 of the control device 21 is disposed in the position as shown in FIG. 2. This means that the vacuum control valve 23 shuts off the communication between the vacuum conduit 28 and vacuum conduit 30 while communicating between the vacuum conduit 30 and outlet 29 to the atmosphere. Therefore, since the pressure within the vacuum conduit 30 is equal to that of the atmosphere, the diaphragm device 20 does not operate so as to close the valve 16. For this reason, the exhaust gas passing through the exhaust port 11 is not introduced through the branch conduit 14, cooling chamber 13, pipe 17 into the conduit 19 as the branched exhaust gas. As a result, the branched exhaust gas is not introduced into the intake gas mixture passing through the inlet manifold 9. Thus, the combustion of the fuel does not become worse so as not to deteriorate the operability of the engine.

Then, if the temperature of the coolant in the engine becomes over a predetermined value such as, for example 60 C., the rod 24 is moved leftwardly by the sensor 22 so as to move the vacuum control valve 23 to the position as shown in FIG. 1. It follows that the vacuum conduit 30 then communicates with the vacuum conduit 28 through the vacuum hole 25 and, at the same time, communication with outlet 29 to the atmosphere is blocked. In such a state, when the vacuum within the vacuum conduit 28 generated by the throttle valve 6 is below a predetermined value such as, for example 1 20 mm. hg., that is, in a decelerating or idling operation or in a low speed low load operation, or the operating state of throttle valve 6 substantially fully opened producing the vacuum within the range A in FIG. 3, the diaphragm device 20 will not operate so that the valve 16 shuts off the communication between the pipe 17 and the conduit 19. Accordingly, the

branched exhaust gas is not introduced into the inlet manifold 9 from the conduit 19.

Since the nitrogen oxide within the exhaust gas is generally very small in the aforementioned two operations, it is not necessary to introduce the branched exhaust gas into the inlet manifold 9.

When the vacuum within the vacuum conduit 28 generated by the throttle valve 6 is over a predetermined value such as, for example l20 mm. hg., that is, in those operating states, except the aforementioned various operations which produce a vacuum in range B in FIG. 3, the diaphragm device 20 operates to open the valve 16. For this reason, after the exhaust gas passing through the exhaust port 11 becomes branched exhaust gas to be fed through the branch conduit 14, cooling chamber 13 and pipe 17 and solid impurities are filtered through the filter 18, it is fed through the pipe 17, valve 16 and conduit 19 and ejected into the inlet manifold 9. The branched exhaust gas ejected into the inlet manifold 9 is mixed with the intake gas mixture resulting in a mixture which has a relatively lowered combustion efficiency to be fed into the operating chambers of the engine. As a result, the nitrogen oxide contained within the discharged exhaust gas is reduced. The detrimental components, such as the carbon monoxide and hydrocarbons, contained within the exhaust gas are thus inversely increased, but they are exhausted into the atmosphere in the exhaust gas in extremely small quantities after being purified within the device 10.

It should be understood from the foregoing description that the device of this invention does not introduce the branched exhaust gas into the intake gas mixture in the warming-up operations of the internal combustion engine. Further, after the warming-up operation of the internal combustion engine, during idling or deceleration of the internal combustion engine or infull load operation, the passage for introducing the branched exhaust gas into the intake gas mixture is closed so that the branched exhaust gas is not introduced into the intake gas mixture while in the other engine operations, except the above specified operations, the above passage is opened so as to introduce the branched exhaust gas into the intake gas mixture.

Accordingly, the branched exhaust gas is introduced into the intake gas mixture only during engine operations that result in a large amount of nitrogen oxide in the exhaust so as to lower the combustion efficiency of the fuel and thus reduce the nitrogen oxide contained within the exhaust gas which is discharged into the atmosphere. Furthermore, since the branched exhaust gas is cooled in the cooling chamber 13 provided in inlet manifold 9 prior to being introduced into valve 16, valve 16 is not deformed by the high temperature of the exhaust gas so as to vastly improve the endurance thereof.

It should also be understood that though the above embodiment is described as a device for purifying the exhaust gas used in a reciprocating piston internal combustion engine, it is not limited only to that application, but may also be applied to other internal combustion engines, such as a rotary piston engine so as to effect the same advantages. It should also be understood that, although the sensor 22 of the control device 21 is controlled by the change of the temperature of the coolant in the engine, this may also be controlled by the change of the temperature of the components of the purifying device 10 provided in the exhaust system or the exhaust gas temperature of the internal combustion engine.

What is claimed is: I

1. A device for purifying exhaust gas of an internal combustion engine for reducing the nitrogen oxide content thereof comprising:

an exhaust conduit for introducing part of the exhaust gas into an intake passage of the engine,

a valve provided in the exhaust conduit opened by a diaphragm device to allow passage of the exhaust gas when the vacuum acting on said diaphragm device becomes over a predetermined value,

a vacuum conduit for introducing the vacuum of the intake passage of a carburetor into said diaphragm device, said vacuum conduit connected to the intake passage at a position adapted to open upstream of a throttle valve when the throttle valve is closed and to open downstream of the throttle valve when the throttle valve is slightly opened, and

control means for operating in sensing the engine temperature and provided in said vacuum conduit, said control means introducing the intake vacuum into said diaphragm device when the sensed temperature is over a predetermined value and shutting off the introduction of the intake vacuum into said diaphragm device when the sensed temperature is below a predetermined value whereby a part of the exhaust gas is introduced into the intake passage only when the engine temperature increases over said predetermined value and the intake vacuum increases over said predetermined value.

2. A device as set forth in claim 1, wherein the exhaust gas introduced into the intake passage is cooled in said exhaust conduit to said valve.

3. A device as set forth in claim v2, wherein a cooling chamber is provided within the intake manifold adjacent to the intake passage in said exhaust conduit to said valve so that the exhaust gas introduced into the intake passage is cooled by utilizing the latent heat of vaporization of the fuel passing through the intake manifold.

l. A device as set forth in claim ll, wherein said control means comprises a casing having a first opening communicating with the intake passage and a second opening communicating with said diaphragm device and a third opening communicating with the atmosphere in a casing, and a control valve operated by a sensor for sensing the engine temperature within said casing, wherein when the engine temperature is below a predetermined value, said second opening and said third opening are connected to each other by said control valve while if the engine temperature increases over said predetermined value, the connection between said second opening and said third opening is shut off so as to connect said first opening to said second opening. 

2. A device as set forth in claim 1, wherein the exhaust gas introduced into the intake passage is cooled in said exhaust conduit to said valve.
 3. A device as set forth in claim 2, wherein a cooling chamber is provided within the intake manifold adjacent to the intake passage in said exhaust conduit to said valve so that the exhaust gas introduced into the intake passage is cooled by utilizing the latent heat of vaporization of the fuel passing through the intake manifold.
 4. A device as set forth in claim 1, wherein said control means comprIses a casing having a first opening communicating with the intake passage and a second opening communicating with said diaphragm device and a third opening communicating with the atmosphere in a casing, and a control valve operated by a sensor for sensing the engine temperature within said casing, wherein when the engine temperature is below a predetermined value, said second opening and said third opening are connected to each other by said control valve while if the engine temperature increases over said predetermined value, the connection between said second opening and said third opening is shut off so as to connect said first opening to said second opening. 